In U. S. Pat. No. 3,926,637 to Bartolini and Bloom which is incorporated by reference herein, permanent volume phase holographic recording is described wherein a hologram is recorded by changing the refractive index of selected areas of a recording medium with coherent light and detecting, also with coherent light, the refractive index changes. The volume phase recording media described comprises certain .alpha.-diketones which are dissolved in a transparent, cured acrylic polyester host. U.S. Pat. No. 3,951,663 to Ross which is incorporated by reference herein describes volume phase holographic recording media of .alpha.-diketones, dissolved in transparent, cured acrylic polyester or epoxy hosts. The copending application of A. Bloom, et al, referred to above and incorporated by reference herein describes volume phase holographic recording media wherein certain .alpha.-diketones are dissolved in sucrose benzoate as the host.
In volume phase recording the recording medium thickness is greater than the recording light wavelength such that the hologram is redundantly recorded in more than one plane in the recording medium. In thin phase recording media, a recording layer has a thickness on the order of the recording light wavelength, so that the hologram records only in one plane.
While the above-described recording media are useful for recording volume phase holograms, they have not been found practical as thin phase recording media.
Negative photoresist polymers containing the .alpha.-diketone benzil, have been described in U.S. Pat. Nos. 3,808,155, 3,865,597, and 3,894,163 to Broyde. In these patents information is recorded by the use of a scanning electron beam in a recording medium which is a negative photoresist. Unlike holographic recording which records with light by modulating the index of refraction in the recording medium, these patents describe recording with electron beams to produce a surface relief pattern in the recording medium. The disadvantages of electron beam-resist methods of recording are that large fluxes of electrons for proper exposure are required and the exposed recording media must be developed before the information can be read.